Chlorine residues in farm milk following the use of two disinfectants of different solubilities.

The incidence of chlorine residues in milk derived from two kinds of chlorine-based disinfectants of differing solubilities was investigated by Wode's test in a total of 420 samples from 30 dairy farms using milk tanks in December 1976 and January 1977. The less soluble of the two disinfectants caused a positive reaction for free chlorine in 4.29 per cent and a weakly positive reaction in 20 per cent of the 210 samples tested. The readily soluble disinfectant caused a weakly positive reaction only, in 3.33 per cent of the samples tested. The difference was statistically significant. In cases where Wode's test gave a positive or a weakly positive reaction, the identification test for antibiotics and chemotherapeutics was made by agar diffusion tests. The results showed that chlorine residues in milk cause small inhibition zones.